Update dependency webpack-dev-server to v3.7.1

Author: renovate-bot

packages/iotex-react-block-producers/package.json

@@ -114,7 +114,7 @@
     "webpack": "4.33.0",
     "webpack-bundle-analyzer": "3.3.2",
     "webpack-cli": "3.3.3",
-    "webpack-dev-server": "3.4.1"
+    "webpack-dev-server": "3.7.1"
   },
   "peerDependencies": {
     "@types/react": "^16.8.15",

packages/iotex-react-footer/package.json

@@ -100,7 +100,7 @@
     "webpack": "4.33.0",
     "webpack-bundle-analyzer": "3.3.2",
     "webpack-cli": "3.3.3",
-    "webpack-dev-server": "3.3.1"
+    "webpack-dev-server": "3.7.1"
   },
   "peerDependencies": {
     "@types/react": "^16.8.11",

packages/iotex-react-language-dropdown/package.json

@@ -104,7 +104,7 @@
     "webpack": "4.33.0",
     "webpack-bundle-analyzer": "3.3.2",
     "webpack-cli": "3.3.3",
-    "webpack-dev-server": "3.4.1"
+    "webpack-dev-server": "3.7.1"
   },
   "peerDependencies": {
     "@types/react": "^16.8.11",